Towards Stable and Conductive Titanium Oxynitride High‐Surface‐Area Support for Iridium Nanoparticles as Oxygen Evolution Reaction Electrocatalyst

Abstract

The rational design of electrochemical oxygen evolution reaction (OER) electrocatalyst is essential for the development of efficient and sustainable electrochemical energy conversion, storage and electrolysis applications. One of the remaining limitations of the low‐temperature electrolyzers is the large amounts of highly scarce and expensive iridium used as the OER electrocatalysts. This could be solved by applying much smaller amounts of iridium on efficient and stable support. Here we present a very promising functionality of titanium oxynitride (TiONx) high‐surface‐area support that effectively disperses the iridium nanoparticles, exhibits good intrinsic electrical conductivity and stability and thus promises efficient reduction of the noble‐metal loading in electrolyzers gas diffusion electrodes. The new nanocomposite made of approximately 3 nm‐sized iridium nanoparticles finely dispersed on TiONx support is produced using a novel synthetic route. Extensive characterization shows that the new composites exhibit an electronic interaction with the support and, ultimately, a high OER performance in acidic media.

Ir/TiONx/C high-performance oxygen evolution reaction nanocomposite electrocatalysts in acidic media: synthesis, characterization and electrochemical benchmarking protocol

“…These results indicate that the SMSI between the TiON x support and Ir nanoparticles most likely inhibits the growth of oxide, which can be electrochemically reduced to more OER-active [55][56][57][58][59][60], lower-valency Ir species. This inhibition of Ir oxide formation was shown in our previous study where Ir on TiON x exhibited the HUPD peaks, specific of metallic iridium, even after cycling until oxidative potential [17]. Thus, the activation protocol should also be optimized for each catalyst, especially for supported ones.…”

“…Thus, much longer exposures and higher temperatures would be necessary, both of which negatively affect the efficiency and usefulness of the synthetic route. By using the beneficial properties of TiO 2 , which is known to be an inherently stable material even under the harsh OER conditions, and TiN, which exhibits a metallic electrical conductivity, stable and conductive support could be achieved [17].…”

“…The 2.6 times higher activity at 1.6 V (6.61 mA/μg Ir and 2.54 mA/μg Ir for our material and the benchmark, respectively) is associated with the better dispersion and thus better utilization of Ir on the high-surface-area support. Moreover, the use of TiON x support with metallic nanoparticles leads to the SMSI effect, which was shown to affect the intrinsic activity of Ir [17].…”

“…Achieving the latter is directly related to the development of sufficiently stable and conductive supports. To increase the utilization, Ir has been supported with stable and conductive oxides such as antimony tin oxide (ATO), indium tin oxide (ITO), titanium oxynitride (TiON x ), etc [13][14][15][16][17]. In addition to the better distribution of Ir on the support's surface, the overall activity can sometimes also be affected by the strong metal-support interaction (SMSI) [18,19].…”

Nanotubular Titanium Oxynitride with an Ultra-Low Iridium Loading as a High-Performance Oxygen-Evolution-Reaction Thin-Film Electrode

“…45 A similar effect has also been noticed in the case of TiON-Ir powder in our previous study. 46 On the other hand, it is important to stress that the average particle size of both analogues is very similar, i.e., 2.29 nm for TiON-Ir and 2.31 nm for Ir Black, see Supporting Information, Sections S5 and S6). Hence, any particle-sizedependent activity effects should be ruled out when comparing the activities of both analogues.…”